1. Field of the Invention
This invention relates to stable compositions of 3-isothiazolones, their preparation, and their use in controlling living organisms.
2. Description of the Prior Art
Isothiazolones have generated high commercial interest as stabilizers against spoilage caused by microorganisms of a large number of aqueous and non-aqueous products subject to such spoilage. Isothiazolones are highly effective and, by suitable choice of the functional groups, broadly useful. However, it was early recognized that either in storage prior to addition to the matrix to be stabilized or after addition, their efficacy was decreased because the isothiazolone was not stable under practical conditions of long-term storage. Means have thus been sought from the beginning of research with such compounds to improve their stability.
U.S. Pat. Nos. 3,870,795 and 4,067,878 teach the stabilization of isothiazolones against chemical decomposition by addition of a metal nitrite or metal nitrate, but teach that other common metal salts, including carbonates, sulfates, chlorates, perchlorates, and chlorides are ineffective in stabilizing solutions of isothiazolones, such solutions usually being in water or in an hydroxylic solvent. Bismuth is not taught or considered in these patents.
U.S. Pat. Nos. 4,150,026 and 4,241,214 teach metal salt complexes of isothiazolones useful because of their enhanced thermal stability, while retaining biological activity. The metal salts listed do not include bismuth.
Japanese Kokai 72-014476 teaches bismuth salts, among other metal salts, of benzisothiazolones useful as bactericidal agents. Such salts would be limited to the structure of the benzisothiazolone where N is substituted with H. Further, the isothiazolones which are not fused to a benzene ring are not considered.
It is known to use certain organic stabilizers for isothiazolones, generally for use situations where metal salts may create problems, such as corrosion, coagulation of latices, insolubility in non-aqueous media, interaction with the substrate to be stabilized, and the like. Formaldehyde or formaldehyde-releasing chemicals are known as stabilizers, (see U.S. Pat. Nos. 4,165,318 and 4,129,448), as are certain organic chemicals such as orthoesters (U.S. application Ser. No. 118,366) and epoxides (U.S. application Ser. No. 194,234).
Grove, U.S. Pat. No. 4,783,221 teaches blends of the isothiazolones of the present invention with at least one metal salt of an organic carboxylic acid of at least six carbon atoms, wherein the metal is a transition metal, zinc, mercury, antimony, or lead, and also with a solvent diluent. The patent is directed to wood preservative compositions and does not teach or suggest use in emulsion stabilization, or paint films applied from said latices, or in metalworking fluids. Further, Grove does not teach or exemplify bismuth.
In certain applications, however, it is desirable to avoid addition of organic stabilizers by virtue of their volatility, decomposition under high heat, higher cost, difficulty in handling, potential toxicity, and the like. Formaldehyde is a suspected carcinogen, and it is desirable not to use formaldehyde in applications where contact with human skin or lungs may occur.
In actual use, copper salts, such as copper sulfate, have proved efficacious in stabilization of isothiazolones. However, copper salts may be undesirable in effluent streams in such operations as in the manufacture of stabilized isothiazolones or in their blending into a product or the use of that product. Copper salts, especially the chlorides, may contribute to possible corrosion, or in the presence of polymers in aqueous dispersion may lead to coagulation of the dispersion.